Loud speaker



Feb. 5, 1963 c. c. FARWELL LOUD SPEAKER Filed May 21, 1959 2 Sheets-Sheet 1 /4 INVENTOR.

pfiAhnv 1 CLAUDE c. FARWELL 42 J /o 1% 7 BY T l l J ATTORNEYS Feb. 5, 1963 c. c. FARWELL LOUD SPEAKER Filed May 21, 1959 FIG.||

2 Sheets-Sheet 2 INVENTOR. CLAUDE C. FARWE LL BY Mm ATTORNEYS United States Patent Ofiice 3,076,520 Patented Feb. 5, 1963 3,076,520 LOUD FEAKER Claude C. Farwell, 6 School St, Groton, Mass. Filed May 21, 1959, Ser- No. 814,792 4 Claims. (Cl. 181-31) This invention relates to a loud speaker for sound reproduction by itself or with accessories. One customary form of loud speaker consists of a conical member to the apex of which is secured a driving member and a voice coil suspended in a constant magnetic field. The coil responds to variations of current in the voice coil to vibrate the cone for the propagation of sound waves.

It is an object of the present invention to add to the effectiveness of the cone by securing to the rim thereof an inverted truncated cone having the same base diameter, thus forming a closed box which is driven as a unit by the voice coil.

It is a further object of the invention to add to the effectiveness of the double cone by mounting in opposition to it a battle board or another similar loud speaker unit.

For a more complete understanding of the invention reference may be had to the following description thereof and to the drawing, of which FIGURE 1 is a perspective view of a cabinet contain ing an embodiment of the invention;

FIGURE 2 is a fragmentary sectional view of the cabinet shown in FIGURE 1;

FIGURE 3 is a sectional view on a larger scale of the speaker shown in FIGURE 2;

FIGURE 4 is an elevational view on a reduced scale of two cabinets having mutually confronting loud speakers mounted therein:

FIGURE 5 is a plan view of the cabinets shown in FIGURE 4 but on a slightly larger scale;

FIGURES 6, 7, 8 and 9 are graphs showing the distribution of intensities of the sound waves from an ordinary loudspeaker cone in directions varying from extreme right to extreme left; and

FIGURES 10, ll, 12 and 13 are graphs showing the distribution of intensities of sound waves from a similar cone on which has been mounted on truncated cone in the manner shown in FIGURE 3.

As indicated in FIGURE 3, my novel speaker comprises a cone of customary construction having a voice coil 12 at the apex thereof. According to the invention, a reversed truncated cone I4 is secured to the cone It), the truncated cone having a base rim In which registers with and is secured to the base rim 18 of the cone It The top 20 of the truncated cone I4 is closed so that the cone In and truncated cone I4- form an air tight container. A compliance ring 22 is secured at the juncture of the rims 16 and 18, the outer periphery of the compliance ring being secured to the margin of a wall 24 which surrounds a hole 25 in the wall. The loud speaker projects through this hole, and, with the compliance ring 22, closes it. For the further support of the speaker, the apex end of the cone It may be attached by means of a small compliance ring 26 to suitable speaker struts 28.

Speakers made in accordance with the invention may come in various sizes. For example, to the cone 10 of a standard 12-inch speaker, which has a base or mouth diameter of 9 /2 inches, a truncated cone I4 is secured with an air-tight joint. The top 20 of the truncated cone has a diameter of 2 /2 inches and a height from the plane of the base or mouth of 2% inches, the slant height of the truncated cone being approximately 4 /2 inches.

The wall 24, as indicated in FIGURE 2 is a part of a cabinet 30 which is closed except for the hole 25 through which the speaker projects. The speaker is mounted so that the compliance ring 22 is in the plane of the wall 24, the cone 10 being within the cabinet 30, the truncated cone 14 projecting outside of the cabinet. When impelled by the excitation of the voice coil 12, the speaker moves as a unit, the sides of the truncated cone 14 propagating sound waves in diverging directions.

This spreading of the sound waves by the double cone, in comparison with the performance of an ordinary cone, is of increasing importance with waves in the intermediate range of frequencies. As indicated by the graphs on the drawings, there is little or no difierence in the case of waves of the order of 250 cycles. As the frequencies increase into the intermediate range, the waves from an ordinary cone become increasingly concentrated in directions close to the axis of the speaker, the intensities dropping off rapidly as the observer moves away from the axis. For example, as indicated in FIGURE 9, waves of frequency of 5000 cycles are almost inaudible to an observer stationed 45 from the axis of the speaker.

With the double cone, however, the Waves of this frequency are more uniformly propagated through a much wider angle from the axis of the speaker.

The radial propagation of sound waves may be assisted and intensified by a baffle plate 32 mounted parallel to the wall 24 and preferably spaced close to the top 20 of the truncated cone. The top 34, bottom 36, and side walls 38 and 44 may extend beyond the end wall 24 and beyond the baffle 32, the area of the latter being less than that of the wall 24 so that there is ample clearance around the periphery of the bafile plate 32.

For more intense radial propagation of sound waves, two closed cabinets 42 and 44 may be mounted in parallel spaced relation as indicated in FIGURES 4 and 5, these cabinets having mutually adjacent, parallel walls 48 and 55 through which, respectively, two loud speakers project, each said loud speaker having a cone 10 within its respective cabinet and a truncated cone 14 in the space between the cabinets. The cabinets may be held in their mutual relationship by any suitable means such as bolts 46. The tops 20 of the loud speakers are parallel and opposite to each other and are spaced a short distance apart. By electrically connecting the two speakers together so that they vibrate in the same phase, sounds of relatively great intensity are produced and are radially propagated from between the mutually confronting cabinets. The intensity of such sounds may be regulated to some extent by adjusting the spacing between the tops 20 of the opposed speakers.

I claim:

1. A loud speaker comprising a hollow cone with a base rim, a hollow truncated cone having a closed top and a base rim registering with and secured to the rim of the first said cone, thereby forming an air-tight container, a support frame, and a compliance ring attached to the entire periphery of said rims at the junction thereof and to said support frame.

2. A loud speaker comprising a hollow cone with a base rim, a hollow truncated cone having a closed top and a base rim registering with and secured to the rim of the first said cone, thereby forming an air-tight container, the top of said truncated cone having a diameter approximately one-fourth of the diameter of the base, a support frame, a compliance ring attached to the juncture of the rims along their entire periphery and to said support frame, and driving means mounted on said container at the apex of the first said cone.

3. A closed cabinet having a wall with a hole therethrough, a loud speaker extending through said hole and comprising a cone and a closed-top truncated cone with base rims mutually registering and secured together to form a tight container, a compliance ring secured to 3 the entire periphery of said rims, the outer periphery of said ring being secured to the wall margin about said hole, and a baffie plate rigidly supported parallel and closely adjacent to the top of said truncated cone.

4. Sound-emitting apparatus comprising two closed cabinets, means holding said cabinets in parallel spaced positions with a wall of one parallel and adjacent to "a wall 'of the other, themutually adjacent walls of said cabinets each-having a loud speaker unit extending therethrough, each said unit including a cone within its cabinet and a closed-top truncated cone outside its cabinet having its base "rim secured to the base of the first said com, the tops or the truncated cones being in close juxtaposition, the space between s'aid'speakers being unobstructed, and means connecting said speaker units to respective walls of said cabinets for the support of said =speaker's.

References Cited in the file of this patent UNITED STATES PATENTS Farrand et al. Sept. 6, 1927 Farrand June 19, 1928 Perow Jan. 1, 1929 George Sept. 13, 1932 Giles "Sept. 5, 1933 DAlton 'Aug. 7, 1934 Leslie -1 Jan. 20, 1959 Irby, Apr. 11, 1961 FOREIGN PATENTS Great Britain, June 10, 1924 

1. A LOUD SPEAKER COMPRISING A HOLLOW CONE WITH A BASE RIM, A HOLLOW TRUNCATED CONE HAVING A CLOSED TOP AND A BASE RIM REGISTERING WITH AND SECURED TO THE RIM OF THE FIRST SAID CONE, THEREBY FORMING AN AIR-TIGHT CONTAINER, A SUPPORT FRAME, AND A COMPLIANCE RING ATTACHED TO THE ENTIRE PERIPHERY OF SAID RIMS AT THE JUNCTION THEREOF AND TO SAID SUPPORT FRAME. 